Gas checks causing fliers

[Bigslug]

I was casting gas check 316299's for my .303's and had some dud bullets on which I wasn't holding the sprue plate down at the hinge pin when I cut them off. The result was that those slugs had a bit of a stem on their bases.

Rather than melt them back down, I decided to make a science project out of them. Seated gas checks through my NOE push-through arrangement as normal, which more or less molded the gas check over the bump, leaving a visibly different base than the slugs that were cut off clean.

10 rounds of clean bases versus the 10 lumpy ones. Same powder charge, same distance, same day:



So yeah. . .square bases matter, and covering their butts with copper doesn't solve the problem.

[Stephen Cohen]

There can be no doubt that bad bases be they cut or just badly cast will result in bad groups, but if you pull back the edge of a check, load and fire it the check will be pushed back into place and all is well again. This was the findings with my 458wm and cast. Regards Stephen

[GregLaROCHE]

What dimension are your unsized boolits? If they are too close to the size you are sizing too, they may not give enough resistance for the check to be forced up tight against the boolits before it is crimped down. If this should be the case and you do not have a larger mold, consider beguiling the mold to get larger boolits.

[toallmy]

What dimension are your unsized boolits? If they are too close to the size you are sizing too, they may not give enough resistance for the check to be forced up tight against the boolits before it is crimped down. If this should be the case and you do not have a larger mold, consider beguiling the mold to get larger boolits.

This is the problem that was causing my lube pressure to push the gas checks off . I have to be very careful with the lube temp and pressure , but I can usually keep it under control .
After I realized some of the gas checks were not fully seated I started seating them before sizing - on a separate press . This plus carefully lube sizing seams to have worked .
I changed the barrel on the rifle recently so I am working out the sizing issues , hopefully the new barrel will like the cast boolits sized down a little more keeping the gas checks on better while handling .
Then I need to keep them on the boollits all the way to the target .

[JMax]

I use two Lee push through sizers for an NOE 314202 GC bullet sized to .314 and .311 and in both cases gas checks are uniform in seating depth and they are square to bullet axis. No flyers have been observed and those checks are on tight.

[GregLaROCHE]

The boolits I gas check are 6.5 mm. I Alox them, then size them with a NOE sizer, putting on the gas check and then Alox them again. To my knowledge, I haven’t have any GCs that weren’t probably installed. My boolit diameter may be less than needed, so I may start beguiling them.

Please let us know what you figure out.

[GregLaROCHE]

Regarding post 21,
If I have a few boolits like that, I rub them on a piece of sandpaper, making sure I keep the bases square.

[beagle]

When I was messing with the .223 and Lyman 225415s, I got flyers. The mould/brand of GCs seems to have an affect on the number of flyers. I took a lot, nose first sized, dropped a dab of super glue in the check and seated in a normal manner. The frequency of the flyers went way down but did not disappear. This was with the Hornaday checks. Best brand I found were the Gators. I'm thinking it's primarily a fit dependent on thickness of metal.

I have a spare 225415 and have been considering removing the GC shank and obtaining a Pat Marlin .22PB check maker and trying that procedure. The PB checks provide a proper fit and the ragged edges seem to "iron into" the bullet base and make them stay on better.

I've heard lube purging theories and seen those test results. I'm thinking we're losing checks.

Felix and I discussed this in depth when he was with us. Lyman designed their checks to possibly come off after exiting the muzzle of in flight and I've observed this. I can't see how the loss of a check would not cause loss of balance and disruption of the bullet's flight path no matter where it departed the bullet.

Just my thoughts./beagle

[earlmck]

I strongly prefer seating gas checks using my push-through (Star) sizer, to the extent that I have now purchased Star dies that duplicate sizes in my old Lyman sizer. The Star doesn't care wheather the bollit base is a bit small or a bit large -- it just flatly seats it. But you do have to have some modest resistance so the check will seat against the base before it begins to be squozed down.

[Dragonheart]

Your thoughts are right on.

Tests on cast bullets 70 years ago proved the slightest deviation in the bullets base affected accuracy.

Have you ever seen the physics experiment where identical projectiles are fired and repeatedly hit the center of a target? Then the next group of projectiles have the projectile's base ground to a specific angle and all fired with the same orientation to the barrel. A new group is formed, but no longer in the canter of the target. By altering the angle of the base the impact point can be calculated.

This is exactly what you are doing, although not intentionally, when your checks are loose, not flat, not round, not perpendicular or not set identical to each other.